A (meth)acrylate having a high refractive index is capable of being used in an optical product, that is, an optical lens, an optical film, an optical media, or the like. In particular, the optical film is capable of being used in a display product such as a liquid crystal display and a plasma display panel, and in particular, is used in a liquid crystal display (LCD) prism sheet, or the like, to improve brightness of a back-light unit disposed in a back side of the liquid crystal display (LCD).
One important optical variable of materials configuring a prism layer of a prism film among the optical films is a refractive index, and as the refractive index is higher, performance of the prism film is improved. As an example of the prism film having the high refractive index used in order to increase efficiency of a LCD backlight, an optical product produced by a polymerizable composition containing a brominated monomer having a high refractive index is disclosed in Korean Patent Laid-Open Publication Nos. 2001-0012340 and 10-2005-0010760. However, halogen compounds such as bromine and chlorine may increase the refractive index. However, after curing, a prepared film has an increase degree of yellowing, the increased yellowing makes the performance of the film deteriorate, and the significantly increased yellowing has an influence on a display color.
That is, currently developed high refractive acrylate contains the halogen compound to be highly toxic, and at the time of combustion, large amounts of corrosive gas are generated. In addition, since a product has a significantly high viscosity or the product is in a state of a solid, at the time of preparing a coating solution, high viscosity is maintained, such that processability thereof has a problem, and since high raw materials are used, a competitive cost is deteriorated.
Therefore, there is a need for preparing a high refractive (meth)acrylate in a liquid state, which is non-halogen and has a relatively low viscosity, by a low cost process.